1 | /* Malloc implementation for multiple threads without lock contention. |
2 | Copyright (C) 2001-2018 Free Software Foundation, Inc. |
3 | This file is part of the GNU C Library. |
4 | Contributed by Wolfram Gloger <wg@malloc.de>, 2001. |
5 | |
6 | The GNU C Library is free software; you can redistribute it and/or |
7 | modify it under the terms of the GNU Lesser General Public License as |
8 | published by the Free Software Foundation; either version 2.1 of the |
9 | License, or (at your option) any later version. |
10 | |
11 | The GNU C Library is distributed in the hope that it will be useful, |
12 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
13 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
14 | Lesser General Public License for more details. |
15 | |
16 | You should have received a copy of the GNU Lesser General Public |
17 | License along with the GNU C Library; see the file COPYING.LIB. If |
18 | not, see <http://www.gnu.org/licenses/>. */ |
19 | |
20 | /* What to do if the standard debugging hooks are in place and a |
21 | corrupt pointer is detected: do nothing (0), print an error message |
22 | (1), or call abort() (2). */ |
23 | |
24 | /* Hooks for debugging versions. The initial hooks just call the |
25 | initialization routine, then do the normal work. */ |
26 | |
27 | static void * |
28 | malloc_hook_ini (size_t sz, const void *caller) |
29 | { |
30 | __malloc_hook = NULL; |
31 | ptmalloc_init (); |
32 | return __libc_malloc (sz); |
33 | } |
34 | |
35 | static void * |
36 | realloc_hook_ini (void *ptr, size_t sz, const void *caller) |
37 | { |
38 | __malloc_hook = NULL; |
39 | __realloc_hook = NULL; |
40 | ptmalloc_init (); |
41 | return __libc_realloc (ptr, sz); |
42 | } |
43 | |
44 | static void * |
45 | memalign_hook_ini (size_t alignment, size_t sz, const void *caller) |
46 | { |
47 | __memalign_hook = NULL; |
48 | ptmalloc_init (); |
49 | return __libc_memalign (alignment, sz); |
50 | } |
51 | |
52 | /* Whether we are using malloc checking. */ |
53 | static int using_malloc_checking; |
54 | |
55 | /* A flag that is set by malloc_set_state, to signal that malloc checking |
56 | must not be enabled on the request from the user (via the MALLOC_CHECK_ |
57 | environment variable). It is reset by __malloc_check_init to tell |
58 | malloc_set_state that the user has requested malloc checking. |
59 | |
60 | The purpose of this flag is to make sure that malloc checking is not |
61 | enabled when the heap to be restored was constructed without malloc |
62 | checking, and thus does not contain the required magic bytes. |
63 | Otherwise the heap would be corrupted by calls to free and realloc. If |
64 | it turns out that the heap was created with malloc checking and the |
65 | user has requested it malloc_set_state just calls __malloc_check_init |
66 | again to enable it. On the other hand, reusing such a heap without |
67 | further malloc checking is safe. */ |
68 | static int disallow_malloc_check; |
69 | |
70 | /* Activate a standard set of debugging hooks. */ |
71 | void |
72 | __malloc_check_init (void) |
73 | { |
74 | if (disallow_malloc_check) |
75 | { |
76 | disallow_malloc_check = 0; |
77 | return; |
78 | } |
79 | using_malloc_checking = 1; |
80 | __malloc_hook = malloc_check; |
81 | __free_hook = free_check; |
82 | __realloc_hook = realloc_check; |
83 | __memalign_hook = memalign_check; |
84 | } |
85 | |
86 | /* A simple, standard set of debugging hooks. Overhead is `only' one |
87 | byte per chunk; still this will catch most cases of double frees or |
88 | overruns. The goal here is to avoid obscure crashes due to invalid |
89 | usage, unlike in the MALLOC_DEBUG code. */ |
90 | |
91 | static unsigned char |
92 | magicbyte (const void *p) |
93 | { |
94 | unsigned char magic; |
95 | |
96 | magic = (((uintptr_t) p >> 3) ^ ((uintptr_t) p >> 11)) & 0xFF; |
97 | /* Do not return 1. See the comment in mem2mem_check(). */ |
98 | if (magic == 1) |
99 | ++magic; |
100 | return magic; |
101 | } |
102 | |
103 | |
104 | /* Visualize the chunk as being partitioned into blocks of 255 bytes from the |
105 | highest address of the chunk, downwards. The end of each block tells |
106 | us the size of that block, up to the actual size of the requested |
107 | memory. Our magic byte is right at the end of the requested size, so we |
108 | must reach it with this iteration, otherwise we have witnessed a memory |
109 | corruption. */ |
110 | static size_t |
111 | malloc_check_get_size (mchunkptr p) |
112 | { |
113 | size_t size; |
114 | unsigned char c; |
115 | unsigned char magic = magicbyte (p); |
116 | |
117 | assert (using_malloc_checking == 1); |
118 | |
119 | for (size = chunksize (p) - 1 + (chunk_is_mmapped (p) ? 0 : SIZE_SZ); |
120 | (c = ((unsigned char *) p)[size]) != magic; |
121 | size -= c) |
122 | { |
123 | if (c <= 0 || size < (c + 2 * SIZE_SZ)) |
124 | malloc_printerr ("malloc_check_get_size: memory corruption" ); |
125 | } |
126 | |
127 | /* chunk2mem size. */ |
128 | return size - 2 * SIZE_SZ; |
129 | } |
130 | |
131 | /* Instrument a chunk with overrun detector byte(s) and convert it |
132 | into a user pointer with requested size req_sz. */ |
133 | |
134 | static void * |
135 | mem2mem_check (void *ptr, size_t req_sz) |
136 | { |
137 | mchunkptr p; |
138 | unsigned char *m_ptr = ptr; |
139 | size_t max_sz, block_sz, i; |
140 | unsigned char magic; |
141 | |
142 | if (!ptr) |
143 | return ptr; |
144 | |
145 | p = mem2chunk (ptr); |
146 | magic = magicbyte (p); |
147 | max_sz = chunksize (p) - 2 * SIZE_SZ; |
148 | if (!chunk_is_mmapped (p)) |
149 | max_sz += SIZE_SZ; |
150 | for (i = max_sz - 1; i > req_sz; i -= block_sz) |
151 | { |
152 | block_sz = MIN (i - req_sz, 0xff); |
153 | /* Don't allow the magic byte to appear in the chain of length bytes. |
154 | For the following to work, magicbyte cannot return 0x01. */ |
155 | if (block_sz == magic) |
156 | --block_sz; |
157 | |
158 | m_ptr[i] = block_sz; |
159 | } |
160 | m_ptr[req_sz] = magic; |
161 | return (void *) m_ptr; |
162 | } |
163 | |
164 | /* Convert a pointer to be free()d or realloc()ed to a valid chunk |
165 | pointer. If the provided pointer is not valid, return NULL. */ |
166 | |
167 | static mchunkptr |
168 | mem2chunk_check (void *mem, unsigned char **magic_p) |
169 | { |
170 | mchunkptr p; |
171 | INTERNAL_SIZE_T sz, c; |
172 | unsigned char magic; |
173 | |
174 | if (!aligned_OK (mem)) |
175 | return NULL; |
176 | |
177 | p = mem2chunk (mem); |
178 | sz = chunksize (p); |
179 | magic = magicbyte (p); |
180 | if (!chunk_is_mmapped (p)) |
181 | { |
182 | /* Must be a chunk in conventional heap memory. */ |
183 | int contig = contiguous (&main_arena); |
184 | if ((contig && |
185 | ((char *) p < mp_.sbrk_base || |
186 | ((char *) p + sz) >= (mp_.sbrk_base + main_arena.system_mem))) || |
187 | sz < MINSIZE || sz & MALLOC_ALIGN_MASK || !inuse (p) || |
188 | (!prev_inuse (p) && ((prev_size (p) & MALLOC_ALIGN_MASK) != 0 || |
189 | (contig && (char *) prev_chunk (p) < mp_.sbrk_base) || |
190 | next_chunk (prev_chunk (p)) != p))) |
191 | return NULL; |
192 | |
193 | for (sz += SIZE_SZ - 1; (c = ((unsigned char *) p)[sz]) != magic; sz -= c) |
194 | { |
195 | if (c == 0 || sz < (c + 2 * SIZE_SZ)) |
196 | return NULL; |
197 | } |
198 | } |
199 | else |
200 | { |
201 | unsigned long offset, page_mask = GLRO (dl_pagesize) - 1; |
202 | |
203 | /* mmap()ed chunks have MALLOC_ALIGNMENT or higher power-of-two |
204 | alignment relative to the beginning of a page. Check this |
205 | first. */ |
206 | offset = (unsigned long) mem & page_mask; |
207 | if ((offset != MALLOC_ALIGNMENT && offset != 0 && offset != 0x10 && |
208 | offset != 0x20 && offset != 0x40 && offset != 0x80 && offset != 0x100 && |
209 | offset != 0x200 && offset != 0x400 && offset != 0x800 && offset != 0x1000 && |
210 | offset < 0x2000) || |
211 | !chunk_is_mmapped (p) || prev_inuse (p) || |
212 | ((((unsigned long) p - prev_size (p)) & page_mask) != 0) || |
213 | ((prev_size (p) + sz) & page_mask) != 0) |
214 | return NULL; |
215 | |
216 | for (sz -= 1; (c = ((unsigned char *) p)[sz]) != magic; sz -= c) |
217 | { |
218 | if (c == 0 || sz < (c + 2 * SIZE_SZ)) |
219 | return NULL; |
220 | } |
221 | } |
222 | ((unsigned char *) p)[sz] ^= 0xFF; |
223 | if (magic_p) |
224 | *magic_p = (unsigned char *) p + sz; |
225 | return p; |
226 | } |
227 | |
228 | /* Check for corruption of the top chunk. */ |
229 | static void |
230 | top_check (void) |
231 | { |
232 | mchunkptr t = top (&main_arena); |
233 | |
234 | if (t == initial_top (&main_arena) || |
235 | (!chunk_is_mmapped (t) && |
236 | chunksize (t) >= MINSIZE && |
237 | prev_inuse (t) && |
238 | (!contiguous (&main_arena) || |
239 | (char *) t + chunksize (t) == mp_.sbrk_base + main_arena.system_mem))) |
240 | return; |
241 | |
242 | malloc_printerr ("malloc: top chunk is corrupt" ); |
243 | } |
244 | |
245 | static void * |
246 | malloc_check (size_t sz, const void *caller) |
247 | { |
248 | void *victim; |
249 | |
250 | if (sz + 1 == 0) |
251 | { |
252 | __set_errno (ENOMEM); |
253 | return NULL; |
254 | } |
255 | |
256 | __libc_lock_lock (main_arena.mutex); |
257 | top_check (); |
258 | victim = _int_malloc (&main_arena, sz + 1); |
259 | __libc_lock_unlock (main_arena.mutex); |
260 | return mem2mem_check (victim, sz); |
261 | } |
262 | |
263 | static void |
264 | free_check (void *mem, const void *caller) |
265 | { |
266 | mchunkptr p; |
267 | |
268 | if (!mem) |
269 | return; |
270 | |
271 | __libc_lock_lock (main_arena.mutex); |
272 | p = mem2chunk_check (mem, NULL); |
273 | if (!p) |
274 | malloc_printerr ("free(): invalid pointer" ); |
275 | if (chunk_is_mmapped (p)) |
276 | { |
277 | __libc_lock_unlock (main_arena.mutex); |
278 | munmap_chunk (p); |
279 | return; |
280 | } |
281 | _int_free (&main_arena, p, 1); |
282 | __libc_lock_unlock (main_arena.mutex); |
283 | } |
284 | |
285 | static void * |
286 | realloc_check (void *oldmem, size_t bytes, const void *caller) |
287 | { |
288 | INTERNAL_SIZE_T nb; |
289 | void *newmem = 0; |
290 | unsigned char *magic_p; |
291 | |
292 | if (bytes + 1 == 0) |
293 | { |
294 | __set_errno (ENOMEM); |
295 | return NULL; |
296 | } |
297 | if (oldmem == 0) |
298 | return malloc_check (bytes, NULL); |
299 | |
300 | if (bytes == 0) |
301 | { |
302 | free_check (oldmem, NULL); |
303 | return NULL; |
304 | } |
305 | __libc_lock_lock (main_arena.mutex); |
306 | const mchunkptr oldp = mem2chunk_check (oldmem, &magic_p); |
307 | __libc_lock_unlock (main_arena.mutex); |
308 | if (!oldp) |
309 | malloc_printerr ("realloc(): invalid pointer" ); |
310 | const INTERNAL_SIZE_T oldsize = chunksize (oldp); |
311 | |
312 | checked_request2size (bytes + 1, nb); |
313 | __libc_lock_lock (main_arena.mutex); |
314 | |
315 | if (chunk_is_mmapped (oldp)) |
316 | { |
317 | #if HAVE_MREMAP |
318 | mchunkptr newp = mremap_chunk (oldp, nb); |
319 | if (newp) |
320 | newmem = chunk2mem (newp); |
321 | else |
322 | #endif |
323 | { |
324 | /* Note the extra SIZE_SZ overhead. */ |
325 | if (oldsize - SIZE_SZ >= nb) |
326 | newmem = oldmem; /* do nothing */ |
327 | else |
328 | { |
329 | /* Must alloc, copy, free. */ |
330 | top_check (); |
331 | newmem = _int_malloc (&main_arena, bytes + 1); |
332 | if (newmem) |
333 | { |
334 | memcpy (newmem, oldmem, oldsize - 2 * SIZE_SZ); |
335 | munmap_chunk (oldp); |
336 | } |
337 | } |
338 | } |
339 | } |
340 | else |
341 | { |
342 | top_check (); |
343 | INTERNAL_SIZE_T nb; |
344 | checked_request2size (bytes + 1, nb); |
345 | newmem = _int_realloc (&main_arena, oldp, oldsize, nb); |
346 | } |
347 | |
348 | DIAG_PUSH_NEEDS_COMMENT; |
349 | #if __GNUC_PREREQ (7, 0) |
350 | /* GCC 7 warns about magic_p may be used uninitialized. But we never |
351 | reach here if magic_p is uninitialized. */ |
352 | DIAG_IGNORE_NEEDS_COMMENT (7, "-Wmaybe-uninitialized" ); |
353 | #endif |
354 | /* mem2chunk_check changed the magic byte in the old chunk. |
355 | If newmem is NULL, then the old chunk will still be used though, |
356 | so we need to invert that change here. */ |
357 | if (newmem == NULL) |
358 | *magic_p ^= 0xFF; |
359 | DIAG_POP_NEEDS_COMMENT; |
360 | |
361 | __libc_lock_unlock (main_arena.mutex); |
362 | |
363 | return mem2mem_check (newmem, bytes); |
364 | } |
365 | |
366 | static void * |
367 | memalign_check (size_t alignment, size_t bytes, const void *caller) |
368 | { |
369 | void *mem; |
370 | |
371 | if (alignment <= MALLOC_ALIGNMENT) |
372 | return malloc_check (bytes, NULL); |
373 | |
374 | if (alignment < MINSIZE) |
375 | alignment = MINSIZE; |
376 | |
377 | /* If the alignment is greater than SIZE_MAX / 2 + 1 it cannot be a |
378 | power of 2 and will cause overflow in the check below. */ |
379 | if (alignment > SIZE_MAX / 2 + 1) |
380 | { |
381 | __set_errno (EINVAL); |
382 | return 0; |
383 | } |
384 | |
385 | /* Check for overflow. */ |
386 | if (bytes > SIZE_MAX - alignment - MINSIZE) |
387 | { |
388 | __set_errno (ENOMEM); |
389 | return 0; |
390 | } |
391 | |
392 | /* Make sure alignment is power of 2. */ |
393 | if (!powerof2 (alignment)) |
394 | { |
395 | size_t a = MALLOC_ALIGNMENT * 2; |
396 | while (a < alignment) |
397 | a <<= 1; |
398 | alignment = a; |
399 | } |
400 | |
401 | __libc_lock_lock (main_arena.mutex); |
402 | top_check (); |
403 | mem = _int_memalign (&main_arena, alignment, bytes + 1); |
404 | __libc_lock_unlock (main_arena.mutex); |
405 | return mem2mem_check (mem, bytes); |
406 | } |
407 | |
408 | #if SHLIB_COMPAT (libc, GLIBC_2_0, GLIBC_2_25) |
409 | |
410 | /* Get/set state: malloc_get_state() records the current state of all |
411 | malloc variables (_except_ for the actual heap contents and `hook' |
412 | function pointers) in a system dependent, opaque data structure. |
413 | This data structure is dynamically allocated and can be free()d |
414 | after use. malloc_set_state() restores the state of all malloc |
415 | variables to the previously obtained state. This is especially |
416 | useful when using this malloc as part of a shared library, and when |
417 | the heap contents are saved/restored via some other method. The |
418 | primary example for this is GNU Emacs with its `dumping' procedure. |
419 | `Hook' function pointers are never saved or restored by these |
420 | functions, with two exceptions: If malloc checking was in use when |
421 | malloc_get_state() was called, then malloc_set_state() calls |
422 | __malloc_check_init() if possible; if malloc checking was not in |
423 | use in the recorded state but the user requested malloc checking, |
424 | then the hooks are reset to 0. */ |
425 | |
426 | #define MALLOC_STATE_MAGIC 0x444c4541l |
427 | #define MALLOC_STATE_VERSION (0 * 0x100l + 5l) /* major*0x100 + minor */ |
428 | |
429 | struct malloc_save_state |
430 | { |
431 | long magic; |
432 | long version; |
433 | mbinptr av[NBINS * 2 + 2]; |
434 | char *sbrk_base; |
435 | int sbrked_mem_bytes; |
436 | unsigned long trim_threshold; |
437 | unsigned long top_pad; |
438 | unsigned int n_mmaps_max; |
439 | unsigned long mmap_threshold; |
440 | int check_action; |
441 | unsigned long max_sbrked_mem; |
442 | unsigned long max_total_mem; /* Always 0, for backwards compatibility. */ |
443 | unsigned int n_mmaps; |
444 | unsigned int max_n_mmaps; |
445 | unsigned long mmapped_mem; |
446 | unsigned long max_mmapped_mem; |
447 | int using_malloc_checking; |
448 | unsigned long max_fast; |
449 | unsigned long arena_test; |
450 | unsigned long arena_max; |
451 | unsigned long narenas; |
452 | }; |
453 | |
454 | /* Dummy implementation which always fails. We need to provide this |
455 | symbol so that existing Emacs binaries continue to work with |
456 | BIND_NOW. */ |
457 | void * |
458 | attribute_compat_text_section |
459 | malloc_get_state (void) |
460 | { |
461 | __set_errno (ENOSYS); |
462 | return NULL; |
463 | } |
464 | compat_symbol (libc, malloc_get_state, malloc_get_state, GLIBC_2_0); |
465 | |
466 | int |
467 | attribute_compat_text_section |
468 | malloc_set_state (void *msptr) |
469 | { |
470 | struct malloc_save_state *ms = (struct malloc_save_state *) msptr; |
471 | |
472 | if (ms->magic != MALLOC_STATE_MAGIC) |
473 | return -1; |
474 | |
475 | /* Must fail if the major version is too high. */ |
476 | if ((ms->version & ~0xffl) > (MALLOC_STATE_VERSION & ~0xffl)) |
477 | return -2; |
478 | |
479 | /* We do not need to perform locking here because __malloc_set_state |
480 | must be called before the first call into the malloc subsytem |
481 | (usually via __malloc_initialize_hook). pthread_create always |
482 | calls calloc and thus must be called only afterwards, so there |
483 | cannot be more than one thread when we reach this point. */ |
484 | |
485 | /* Disable the malloc hooks (and malloc checking). */ |
486 | __malloc_hook = NULL; |
487 | __realloc_hook = NULL; |
488 | __free_hook = NULL; |
489 | __memalign_hook = NULL; |
490 | using_malloc_checking = 0; |
491 | |
492 | /* Patch the dumped heap. We no longer try to integrate into the |
493 | existing heap. Instead, we mark the existing chunks as mmapped. |
494 | Together with the update to dumped_main_arena_start and |
495 | dumped_main_arena_end, realloc and free will recognize these |
496 | chunks as dumped fake mmapped chunks and never free them. */ |
497 | |
498 | /* Find the chunk with the lowest address with the heap. */ |
499 | mchunkptr chunk = NULL; |
500 | { |
501 | size_t *candidate = (size_t *) ms->sbrk_base; |
502 | size_t *end = (size_t *) (ms->sbrk_base + ms->sbrked_mem_bytes); |
503 | while (candidate < end) |
504 | if (*candidate != 0) |
505 | { |
506 | chunk = mem2chunk ((void *) (candidate + 1)); |
507 | break; |
508 | } |
509 | else |
510 | ++candidate; |
511 | } |
512 | if (chunk == NULL) |
513 | return 0; |
514 | |
515 | /* Iterate over the dumped heap and patch the chunks so that they |
516 | are treated as fake mmapped chunks. */ |
517 | mchunkptr top = ms->av[2]; |
518 | while (chunk < top) |
519 | { |
520 | if (inuse (chunk)) |
521 | { |
522 | /* Mark chunk as mmapped, to trigger the fallback path. */ |
523 | size_t size = chunksize (chunk); |
524 | set_head (chunk, size | IS_MMAPPED); |
525 | } |
526 | chunk = next_chunk (chunk); |
527 | } |
528 | |
529 | /* The dumped fake mmapped chunks all lie in this address range. */ |
530 | dumped_main_arena_start = (mchunkptr) ms->sbrk_base; |
531 | dumped_main_arena_end = top; |
532 | |
533 | return 0; |
534 | } |
535 | compat_symbol (libc, malloc_set_state, malloc_set_state, GLIBC_2_0); |
536 | |
537 | #endif /* SHLIB_COMPAT */ |
538 | |
539 | /* |
540 | * Local variables: |
541 | * c-basic-offset: 2 |
542 | * End: |
543 | */ |
544 | |